613
FXUS66 KMTR 240827
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
1227 AM PST Mon Nov 24 2025

...New SHORT TERM, LONG TERM...

.KEY MESSAGES...
Updated at 1226 AM PST Mon Nov 24 2025

 - Dry and mild this week with stratus overnight and through the
   morning

 - Cooler temperatures this weekend as the next system approaches

 - Confidence increasing for gusty offshore winds by the end of
   the upcoming weekend

&&

.SHORT TERM...
Issued at 1226 AM PST Mon Nov 24 2025
(Today and tonight)

The stratus layer envelops most of the Bay Area valleys and extends
in to the Monterey Bay and Salinas Valley regions, with the
expectation that the layer continues to build through the night
somewhat undercut by the clearing of the Santa Rosa Plain. Will
monitor how the stratus evolves through the night, but will hold
firm on seeing a general expansion of the stratus layer through the
rest of the morning. A more pressing question will be how dense fog
evolves through the next several hours. At this point the only
station that has consistently reported dense fog (1/4 mi visibility
or less) is Byron in the southeastern corner of Contra Costa County,
with trends across the Central Valley suggesting that dense fog is
also present across the eastern tier of Contra Costa County (east of
the Diablo Hills, including the Antioch area). Fog has also been
reported across other regions of the Bay Area, including Concord and
Novato, but we have not seen the widespread dense fog anywhere that
would trigger a Dense Fog Advisory. If observations show more
widespread fog development, one may need to be issued later this
morning. For those morning commuters who do encounter dense fog,
slow down, use low-beam headlights, and allow extra distance between
you and the car in front of you. In any case, stratus should begin
to dissipate sometime after sunrise and be generally cleared out by
the afternoon.

The weather pattern remains largely similar to yesterday`s with a
weak ridge aloft and a gentle onshore flow this afternoon. High
temperatures range from the middle to upper 60s in the inland
valleys to the upper 50s to middle 60s across the coastal and
Bayside regions.

&&

.LONG TERM...
Issued at 1226 AM PST Mon Nov 24 2025
(Tuesday through Sunday)

A building ridge aloft brings a gradual warming trend for Tuesday
into Thanksgiving (Thursday), compressing the marine layer and
raising temperatures by a few degrees, with the rise in temperatures
somewhat balanced out by some cold air advection stemming from an
interaction between a building high in the east Pacific and a
building low in the Desert Southwest. The warmest spots of the
inland valleys (think the Morgan Hill-Gilroy region and the southern
Salinas Valley) might touch the lower 70s on Wednesday and Thursday.

Towards Friday into the upcoming weekend, a pattern change will
occur as the ridge over the western United States breaks down, and
one amplifies upstream across the Gulf of Alaska. As a result, cold
Arctic air descends into the Mountain West and Central Plains
states. Ensemble model guidance continues to point to this system
following more of an inside slider like development in our region.
In other words, the impacts of this trough fall into the windy and
dry side rather than the rainy side. Still too early to tell how
strong the impacts will be and where the greatest threats will
occur, but the current forecast has a period of gusty offshore winds
developing across the Bay Area and Central Coast late Saturday
through, and somewhat beyond, the end of the 7-day forecast period.
Confidence in the exact nature of the impacts will improve through
the rest of the week, so keep in touch with the forecast updates for
the most up to date information.

&&

.AVIATION...
(06Z TAFS)
Issued at 1000 PM PST Sun Nov 23 2025

The inland stratus intrusion has momentum to it this evening,
from a surface pressure perspective SFO-WMC and SFO-SAC gradients
are both weakly onshore (vs 24 hours ago WMC-SFO was 5.5 mb).
Satellite, surface observations including a recent spotter report
from Pleasant Hill indicate stratus ceilings and onshore winds are
to some extent along the leading edge blending in with the western
edge of tule fog /VLIFR/ that is in parts of the East Bay. A lower
level cyclonic circulation with drier air is also intruding in along
the back side of the stratus along the coastline at least temporarily
mixing out the stratus.

Observations are still VFR-MVFR over the forecast area except IFR-
LIFR due to residual evening stratus and fog in the East Bay and the
North Bay. As mentioned, cooler air from the surface to lower levels
continues to filter in from the west and northwest, ceilings tonight
and Monday morning will be a mix of MVFR and IFR-LIFR including
possibly VLIFR in dense fog. The 00z (4 pm PST) Oakland sounding,
much like this morning`s 12z sounding, showed a lower level subsidence
temperature inversion based near 1500 feet; cooler air remains well
entrenched under the temperature inversion with additional cooler air
arriving tonight and Monday morning per NAM output (with additional
loss of heat to space via radiative cooling where it`s initially
dry/clear sky). For tomorrow HREF shows clearing by 21z (1 pm PST)
across the Bay Area, suggesting improving mixing may result in earlier
mix out times compared to today.

Vicinity of SFO...Currently it`s back to VFR with a dry air
intrusion from the north. Best guess is that night-time cooling
and cool air advection will help redevelop a stratus ceiling with
tempo MVFR 06z-10z then MVFR prevailing until 20z Monday. West
wind 10 knots decreasing to light westerly wind then near 10 knots
Monday afternoon and evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...MVFR-IFR tonight and Monday morning. VFR
by late morning and early afternoon Monday. Light and variable winds
to light southeasterly winds tonight and Monday morning, then shifting
to onshore 5 to 10 knots Monday afternoon and early evening.

&&

.MARINE...
(Tonight through next Saturday)
Issued at 859 PM PST Sun Nov 23 2025

High pressure will persist over the coastal waters through mid and
late week. Seas will gradually ease Monday through the middle of
the week with gentle to moderate northerly breezes. Winds begin to
increase along with building seas by the end of the week and into
next weekend.

&&

.BEACHES...
Issued at 614 PM PST Sun Nov 23 2025

A Beach Hazards Statement is in effect through Monday evening. A
long period northwesterly swell will result in an increased risk
for sneaker waves and rip currents. Breaking waves of 13 to 18
feet are expected. Sneaker waves can unexpectedly run
significantly farther up the beach than normal, including over
rocks and jetties. Rip currents are typically more frequent and
stronger in the vicinity of jetties, inlets, and piers.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement through this evening for CAZ006-505-509-
     529-530.

PZ...Small Craft Advisory until 3 AM PST early this morning for
     Pigeon Pt to Pt Pinos 10-60 NM.

&&

$$

SHORT TERM...DialH
LONG TERM....DialH
AVIATION...Canepa
MARINE...Canepa

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